(CNN) -- Yemen told outside powers Wednesday to stay out of its battle with a Shiite rebel group in its northwest amid concerns that Iran and Saudi Arabia are being drawn into the conflict.

The statement, carried by the state news agency Saba and attributed to a Foreign Ministry source, followed a statement of concern for Yemen's "national unity and territorial integrity" by Iranian Foreign Minister Manouchehr Mottaki on Tuesday.

"We welcome what Mottaki affirmed about Iran's position towards Yemen's unity and stability, and Yemen reaffirms that it definitely rejects the interference in its internal affairs by any party," the statement said. It said Yemen's battle with the Houthi, a Shiite Muslim rebel movement, is "an internal Yemeni affair, and Yemen can solve its issues without any interference from others."

Battles between Yemeni government forces and rebels have raged intermittently for five years, and government troops launched a new offensive in late summer. Saudi Arabia, Yemen's northern neighbor, turned its air force against suspected Houthi rebels last week after it said the rebels had crossed into Saudi territory.

The Houthi claimed that the airstrikes occurred within Yemeni territory, a claim both the Saudi and Yemeni governments denied.

The persistent fighting has raised concerns that Yemen -- where U.S. officials say al Qaeda is attempting to establish a new foothold in the region -- could be the stage for a proxy struggle between Shiite-dominated Iran and the Sunni-led Saudi monarchy. Yemen says the conflict is about reasserting government authority and is not a sectarian war.

Yemen has accused Iran of supporting the rebels. A Yemeni government official told CNN on Tuesday that Yemen's navy was "on the highest state of alert" after an Iranian boat was captured near Yemeni and Saudi territorial waters last week.

In Washington, however, a senior State Department official told CNN that although the U.S. government is concerned about the Yemeni conflict it does not see any sign of an Iranian hand in the Houthi revolt.

The State Department has been in touch with the Yemenis and Saudis about the need to reduce tensions but is yet to be convinced that Iran is involved in Yemen, the official said.

The United Nations has expressed alarm over the fighting and said there has been a "significant increase" in the number of people displaced in recent weeks. The U.N. High Commissioner for Refugees estimates as many as 175,000 people have been affected by the conflict since 2004, U.N. spokesman Farhan Haq said Tuesday.